Generally, a film heater is made by two methods. According to one method, a conductive material, such as carbon, having a predetermined resistance, is coated on an insulator in a predetermined pattern, so that the heater generates heat by applying a current to the conductive pattern. According to the other method, an electrically resistive wire, such as carbon wire or nichrome wire, is mixed as woof threads or warp threads when weaving a fabric using fibers, thereby producing a heating fabric element, so that the heating fabric element generates heat by applying a current to the electrically resistive wire.
A heating fabric having a heating fabric element is shown in FIGS. 1 and 2. Referring to FIG. 1, the heating fabric comprises a fabric made by weaving regular fibers, such as natural fibers or synthetic fibers 35, as woof threads 21 and warp threads 22, close to each other, a heating fiber 13, such as carbon fiber, arranged in the fabric at predetermined intervals, as warp threads 22, and a metal fiber 27 woven to extend from both side edges of the fabric as warp threads 22. Further, a power line 15 is connected to one edge of the woven metal fiber 27 to supply electric power to the fabric. The carbon fibers and the nichrome wires used generally in the heating fabric as the metal fibers are not easily fused and attached to lead used as the power line 15. Accordingly, the conductive part 32 made of the metal fibers 27 is connected to the power line 15 by using a double-side press terminal 18 which is in contact with both sides of the conductive part 32 and pressed against the conductive part 32 from both sides of the conductive part 32.
By the connection method using the double-side press terminal, current conduction can be easily caused between the power line and the conductive part, which is made by weaving metal fibers. However, the connection method using the double-side press terminal also has the disadvantage of a short circuit, which can easily occur due to the press. Accordingly, even though the terminal is compressed, the connection is not always successful, so that contact resistance at the contact portion between the conductive part and the power line increases. As a result, the heating fibers are separated from the press terminal and a short circuit is caused at the side edges of the terminal due to the press applied to the press terminal, so that the function of the heating fabric can not be properly performed and product failure is caused, resulting in degradation of the product reliability and increase in after-service demands.
Further, in the case in which the power line 15 is connected to the heating fiber 27 in parallel, since contact points to be connected in parallel are connected by an electric wire, such as heat resistant wire, the productivity of electronic heaters using a heating fabric element, such as an electronic heating pad or an electronic heating mat, is lowered, and emission of electromagnetic wave is increased since the direction of current flows in the two adjacent electric wire groups are the same.